This invention relates to heat conducting devices, and more particularly to a heat conducting device for a circuit board.
A circuit board (CB) located in a missile contains electronics mounted on and through the CB. The electronics themselves generate heat, and the CB may also experience an influx of aerodynamic heat through the airframe of the missile during high speed flight. Both internal and external sources of heat may degrade the operation of the CB and the electronics.
In many older missiles, the influx of heat during high speed flight was the primary concern because the electronics did not produce large amounts of heat. Accordingly, missiles that had short duration high speed flights were designed to limit the influx of heat during that mode of operation. These designs, however, did not allow for the removal of heat from the missile. Thus, as the electronics have become more complex and have begun to operate for longer periods of time, internal heat has become a concern too. Thus, CBs in some modern missiles may generate significant internal heat and also experience significant heating from the airframe during high speed flight.
The present invention substantially reduces or eliminates at least some of the disadvantages and problems associated with circuit boards (CBs) in missiles. The present invention can provide a heat conducting device with a low impedance thermal path for the heat generated by the electronics on the CB in one mode of operation of the missile and a high impedance thermal path for the heat generated by the aerodynamics on the airframe in another mode of operation of the missile.
In one embodiment of the present invention, a heat conducting device for providing a thermal path between a circuit board and an airframe includes a thermal plane adapted to receive a circuit board and a collar encompassing at least a portion of the thermal plane. The collar has a first position to disengage from at least a portion of the airframe and a second position to engage at least a portion of the airframe to provide a thermal path between the circuit board and the airframe.
In another embodiment, a method for providing a thermal path between a circuit board and an airframe includes mounting a circuit board on a thermal plane and disposing a collar around at least a portion of the thermal plane. The method also includes placing the collar in a first position to disengage from at least a portion of the airframe and placing the collar in a second position to engage at least a portion of the airframe to provide a thermal path between the circuit board and the airframe.
The present invention has several important technical features and advantages. First, because the outside perimeter of the heat conducting device contracts when the collar is placed in the disengaged position, the collar allows for efficient insertion of the heat conducting device into a missile when being assembled. Second, the collar and, hence, the heat conducting device engaging with at least a portion of the airframe when the collar is in the engaged position provides a low impedance thermal path between the CB and the airframe for the heat generated by the electronics on the CB during one mode of operation of a missile, such as during captive flight of an air-to-air missile. The heat conducts through the thermal plane and the collar to the airframe, where it discharges to the ambient surroundings. In certain embodiments, the collar can again be placed in the disengaged position, which raises the impedance of the thermal path between the CB and the airframe during another mode of operation of a missile, such as high speed free flight of an air-to-air missile. This protects the CB and the electronics from influxing aerodynamic heat.
In a particular embodiment, the thermal plane has a shape similar to a lateral cross-section of the missile, allowing the CB and the thermal plane to mount perpendicular to the longitudinal axis of the missile. This shape allows for a more uniform design of the heat conducting devices and the CBs and provides a more structurally sound support for the CBs, compared to CB mountings parallel to the longitudinal axis of the missile.
In further embodiments, multiple heat conducting devices can couple together to form an assembly of heat conducting devices before insertion into a missile, during assembly or when the electronics are being repaired and reinstalled. This permits efficient interconnection between the electronics on CBs on different heat conducting devices in the assembly. As before, placing the collars in the disengaged position allows for efficient insertion of the heat conducting devices in the assembly into the missile. After mounting the assembly in the airframe, placing the collars, individually or as a group, in the engaged position engages them with at least a portion of the airframe, providing a low impedance thermal path for the heat generated by the electronics on the CBs during one mode of operation of a missile. In some of these embodiments, an actuator disengages all of the collars in the assembly from at least a portion of the airframe during another mode of operation of a missile.
In a particular embodiment, the heat conducting devices in the assembly can move laterally to the longitudinal axis of the missile independently of each other when the collars are disengaged. Thus, the heat conducting devices can independently center when engaging the airframe.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, description, and claims.